Having said all that about the RB-211, I was told that RR orginally did, and / or planned to certify it on the 747 without deicing it. P&W / GE objected ( unfair compedative advantage etc. due to the aforementioned fuel issues ) so RR relented, and certified it with. The spinner explanation seems plausable, but what about the ice forming on the nacelle. Anyone have anymore background on this?